pub fn printGrades(idx: libc::c_int) {
    unsafe {
        libc::printf(b"Student grades:\n\0".as_ptr() as *const libc::c_char);
        libc::printf(
            b"Student %d: %d\n\0".as_ptr() as *const libc::c_char,
            idx,
            grades[(idx - 1) as usize],
        );
    }
}
